1. Field of the Invention
The present invention relates to an apparatus for applying at least one magnetizable dispersion containing pigments and polymeric binders to the front of a linearly transported nonmagnetic substrate by means of an extrusion coater, the orifice of the slot transporting the dispersion being essentially opposite the edge of the pole surface of a magnet arranged adjacent to the back of the substrate.
2. Description of the Prior Art
Apparatuses of the abovementioned generic type are disclosed, inter alia, in DE-B-19 07 212, DE-A-42 26 139 and German Patent Application P 44 43 896 of the same Applicant. A major advantage of this coating arrangement is that the applied amount of dispersion depends only on the dose supplied but, within certain limits, is independent of the distance from the extruder orifice to the substrate. As is evident from the example of the abovementioned DE-B-19 07 212, coating speeds of 100 m/min can thus readily be achieved.
Recently, substantially higher coating speeds have been required for greater cost-efficiency of the coating procedure and in addition the magnetic properties of magnetic recording media thus achieved must meet higher requirements; in particular the smoothness of the surface should be improved to achieve constant contact between the head and the magnetic recording medium.